let _Vue = null

export default class VueRouter {
  constructor (options) {
    this.options = options
    this.data = _Vue.observable({
      current: "/"
    })
    this.routeMap = {}
  }

  static install (Vue) {
    // 1. 判断插件是否已经被安装
    if (VueRouter.install.installed) return
    VueRouter.install.installed = true
    // 2. 将Vue实例保存在全局中
    _Vue = Vue
    // 3. 把创建Vue实例时传入的router对象注入到Vue实例上
    _Vue.mixin({
      beforeCreate () {
        if (this.$options.router) {
          _Vue.prototype.$router = this.$options.router
          this.$options.router.init()
        }
      }
    })
  }

  init () {
    this.createRouteMap()
    this.initComponents(_Vue)
    this.initEvent()
  }

  createRouteMap () {
    this.options.routes.forEach(route => {
      this.routeMap[route.path] = route.component
    })
  }

  initComponents (Vue) {
    Vue.component('router-link', {
      props: ['to'],
      render (h) {
        if (this.$router.options.mode === "history") {
          return h('a', {
            attrs: {
              href: this.to
            },
            on: {
              click: this.handleClick
            }
          }, [ this.$slots.default ])
        } else if (this.$router.options.mode === "hash") {
          return h('a', {
            attrs: {
              href: "#" + this.to
            },
          }, [ this.$slots.default ])
        }
        
      },
      methods: {
        handleClick (e) {
          history.pushState({}, '', this.to)
          this.$router.data.current = this.to
          e.preventDefault()
        }
      }
    })

    Vue.component('router-view', {
      render: (h) => {
        const component = this.routeMap[this.data.current]
        return h(component)
      }
    })
  }

  initEvent () {
    window.addEventListener("load", () => {
      if (this.options.mode === "history") {
        this.data.current = this.data.current || "/"
      } else if (this.options.mode === "hash") {
        this.data.current = window.location.hash ? window.location.hash.slice(1) : "#/"
      }
    })
    if (this.options.mode === "history") {
      window.addEventListener('popstate', () => {
        this.data.current = window.location.pathname
      })
    } else if (this.options.mode === "hash") {
      window.addEventListener("hashchange", () => {
        console.log(window.location.hash);
        this.data.current = window.location.hash.slice(1)
      })
    }
  }
}